The semiconductor substrate in large scale integrated circuit chips must be maintained at a predetermined voltage relative to the active portions of the circuit, in order to establish a suitable reference for the generation and processing of signals by the integrated circuit. Existing substrate voltage generator circuits typically provide approximately 20 microamperes as a maximum charging current to the substrate. As the device count and density of integrated circuits becomes greater, the amount of diffusion leakage current out of the substrate becomes significant. In order to maintain the desired substrate voltage for very large scale integrated circuits, the size of the substrate voltage generator circuit must be increased, consuming larger quantities of precious real estate on the integrated circuit chip. Typical of such prior art substrate voltage generator circuits include those disclosed in U.S. Pat. Nos. 3,790,812; 3,806,741; and 4,208,595. Although these prior art circuits may have worked well for lower density integrated circuit applications where the diffusion leakage currents are relatively small, they cannot meet the significantly higher substrate charge pumping requirements of modern VLSI integrated circuit chips without increased use of chip real estate.